Two types of these objects were delineated by Abrikosov with respect to one model, whose namesake parameter is the ratio of the penetration depth to the coherence length. The 
Two types of these objects were delineated by Abrikosov with respect to one model, whose namesake parameter is the ratio of the penetration depth to the coherence length. The free energy of these objects is minimized when the Laplacian of H equals the negative square of the London penetration depth times H, a condition that results in a form of perfect (*) diamagnetism unrelated to the expected Lenz's law cancellation. These materials may be modeled by Ginzberg-Landau theory or by constructing a superfluid of bosons called Cooper pairs. YBCO is a high-temperature example of these materials, which expel magnetic fields in the Meissner effect. BCS theory governs, for 10 points, what materials that exhibit zero electrical resistance?
Two types of these objects were delineated by Abrikosov with respect to one model, whose namesake parameter is the ratio of the penetration depth to the coherence length.
{superconductors} [{or superconductivity}; {accept word forms}]